The present invention relates to the art of automatic control systems. It finds particular application in conjunction with the control of building maintenance functions, particularly coordinated and combined control of water treatment and energy usage facilities and will be described with reference thereto. It is to be appreciated, however, that the invention also finds other applications including automatic maintenance of boiler, cooling tower water chemistry, control of water treatment chemistry, control of chemical processing chemistry, control of chemical manufacturing, and the like.
Heretofore, various computer based controllers have been developed for monitoring and managing the electrical energy usage of office buildings and the like. However, the treatment of water in the cooling tower was left substantially to human control. Inept and unskilled human management of the cooling tower or boiler water has frequently resulted in unnecessary expense and a loss of efficiency.
Cooling tower water and boiler water need periodic chemical adjustment to provide efficient cooling and heat transfer. For example, biocides are added to kill algae and other organisms that breed in the warm water. As the warm water evaporates, the concentration of calcium, magnesium, and other water dissolved chemicals which tend to coat and insulate heat transfer apparatus increases reducing heat transfer efficiency. The deposition of calcium and magnesium is fought by the periodic bleeding and replacement of the high dissolved chemical concentration water and by the addition of deposition inhibiting chemicals. Other chemicals are commonly added to inhibit corrosion, adjust pH, complex suspended particulates, and the like.
Equipment has been developed for monitoring these and other chemical properties. However, the addition of appropriate amounts of chemicals is commonly left to human operators and human error. In many instances, the human operators are general building maintenance personnel that are untrained in water treatment chemistry and procedures. Money was wasted by adding too much of some water treatment chemicals, while cooling or heating efficiency were cut by adding too little of others.
To reduce the required human maintenance and accompanying human error, others have suggested apparatus for the automatic addition of chemicals and the automatic bleeding of a percentage of the cooling water. However, this equipment too was subject to failure. When chemical additive pumps or valves stuck in a feed state, large amounts of treatment chemicals were wastefully added until the supply drum went dry. Thereafter, the treatment chemical was unavailable for addition until the next scheduled supply drum replacement. The addition of unnecessary chemicals is financially wasteful, not only in the cost of excess chemicals but also in the loss of heat transfer efficiency. When the treatment chemical addition pumps or valves failed in a flow blocking state, the supply drums ran dry, or bleed valves stuck closed, heat transfer efficiency was reduced. When bleed valves are stuck open, excessive water removal could irrepairably damage the entire system.
The present invention contemplates a new and improved control system which automatically monitors water quality, such as conductivity, pH, temperature, chemical quantity on hand, impurities, and the like. Appropriate provision is made for adjusting the chemical composition of the water to maintain the water quality within selected ranges and to guard against system malfunction.